To ensure maximum braking deceleration of the motor vehicle within the shortest possible time during emergency braking, methods for evaluating an intent of the driver to decelerate and for increasing operating pressure in a brake system are known in which, depending on the rate of pressure buildup in the hydraulic system, an additional pressure boost is provided to allow more rapid pressure buildup, and thus maximum deceleration, to be achieved.
These conventional braking assistance (BA) systems are usually based on a modified brake power booster having additional electrical components, or on a hydraulic unit of a traction control system (TCS) or electronic stability program (ESP) in which the pressure in the master brake cylinder is increased, as needed, by electrical actuation of valves, as a function of a brake pedal travel and/or a change of the pedal travel and/or of the master brake cylinder pressure over time. A certain additional design complexity of the hydraulic system is required to detect these referenced variables and to activate the additional components.
A method for controlling a hydraulic brake power booster for a brake pressure control device is described in German Patent Application No. DE 199 25 794 A1 in which a triggering point is determined at which a hydraulic unit for boosting the brake pressure is activated and/or deactivated, taking into account a derivation over time of a master cylinder pressure and a differential pressure between the pressure in a partial vacuum chamber and/or a working chamber of an automatic brake power booster, and the ambient pressure. This is intended to allow a braking response, even for various braking dynamics (pedal actuation rate), which optimally meets the requirements for pedal comfort, ability to proportion the braking force, and safety.